Page 41
MSL600
Installation, Operation & Maintenance Manual
IP262/Z0, Rev. AB
February 2012
7.9.3.5 Noise SD Mult – P635
The Municipal 1 algorithm scans the echo profile for echoes. Prior to sending pulses to the transducer, the
noise floor is measured. It calculates the mean and standard deviation of fluctuations in the noise floor.
In order to be significant, the echo from a blanket must not only exceed a threshold value determined in terms of
the standard deviation of the echo amplitudes (P634) but it must also exceed a threshold value determined in
terms of the standard deviation of the noise floor (P635).
The default value is 2.75 standard deviations.
Parameter values:
Default Min Max
2.75 0.00 9.99
7.9.3.6 Dirty Mult – P636
It is often the case that the supernatant becomes dirty. In this case, large echoes can be seen directly in front of
the transducer that should not necessarily be ignored or blanked out. If the amplitude of these signals is typically
above 50% of the screen width, it is likely the supernatant was dirty and an alarm would be helpful in this
situation. This can be achieved by programming a relay to operate in alarm mode and setting the alarm
condition to Dirty S-nat.
Parameter P636 is used to linearly scale the default threshold of 50%. The default value is a multiplier of 0.5,
which represents 50% of the maximum displayable amplitude.
Parameter values:
Default Min Max
0.5 0.00 2.00
7.9.3.7 Lost Echo Time - P637
The Municipal 1 algorithm has a facility such that if the echo is lost from a set range (see P633) then the last
reading is held for the programmed time. This allows the unit to accommodate any false echoes from targets
other than the sludge blanket. In other words, the device is able to recognise that the sludge level does not
change rapidly.
The parameter can be set between 1 to 255 minutes
Parameter values:
Default Min Max
30 1 255
